Embodiments of the invention generally relate to apparatus and methods of holding a substrate during processing. In particular, embodiments of the invention are directed to lift pins for loading and unloading wafers from a processing chamber and methods of use.
In some CVD and ALD processing chambers, the substrates, also referred to herein as wafers, move relative to the precursor injector and heater assembly. If the motion creates acceleration forces larger than that of the frictional force, the wafer can become displaced causing damage or related issues. The wafers placed off-axis can slip at high acceleration/deceleration on a moving/rotating susceptor. Friction from the weight of the wafer itself is insufficient to hold the wafer on tools where higher throughput is sought.
To prevent the rotational forces from dislodging the wafer during process, additional hardware to clamp or chuck the wafer in place may be needed. For example, vacuum chucking may be incorporated into susceptor to provide negative pressure to the bottom surface of a wafer.
In single wafer processing chambers, wafers often preheat while resting on lift pins before being loaded into the susceptor recess. In carousel processing chambers, the preheating occurs at a loading position because the susceptor rotates. This process takes time and results in delays in indexing and loading of the next wafer. The susceptor of a carousel processing chamber has to stop rotation for an extended period of time to load each wafer. This delay in processing is cumulative and can result in large amounts of lost time.
Therefore, there is a need in the art for apparatus and methods to increase the wafer loading speed and shorten the delay for wafer pre-heating in processing chambers.